It's very good for an idea to be commonplace. The important thing is that a new idea should develop out of what is already there so that it soon becomes an old acquaintance. Old acquaintances aren't by any means always welcome, but at least one can't be mistaken as to who or what they are.

More than that, I believe that the grass is green because green is restful to the human eye, that the sky is blue to give us an idea of the infinite. And that blood is red so that murder will be more easily detected and criminals will be brought to justice. Yes, and I believe that I shall live forever, but I shall live without reason.

I have remained true to my deepest convictions. I mean the courage of those who are born to be defeated, the weaknesses of the strong, and the tragedy of misunderstandings and missed opportunities, which I have done my best to treat as comedy—for otherwise how can we manage to bear it?

Duty is what no-one else will do at the moment.

If they don't depend on true evidence, scientists are no better than gossips.

Morality is seldom a safe guide for human conduct.

An unjust punishment is never forgotten.